Process for producing sputtered films

ABSTRACT

A PROCESS FOR PRODUCING SPUTTERED FILMS AND AN APPARATUS FOR CARRYING OUT SAID PROCESS IN WHICH SUBSTRATES ARE TRANSFERRED BETWEEN A SPUTTERING CHAMBER AND ONE OF AT LEAST TWO PRELIMINARY CHAMBERS BOTH OF WHICH SPUTTERING AND ONE PRELIMINARY CHAMBERS ARE MAINTAINED UNDER THE SAME PRESSURE AND GAS ATMOSPHERIC CONDITIONS, SAID SUBSTRATES ARE SPUTTERED FILMS THEREON WHILE THEY ARE DISPOSED IN THE SPUTTERING CHAMBER AND DURING THE TRANSFER AND SPUTTERING OF SAID SUBSTRATES THE OTHER OF SAID PRELIMINARY CHAMBERS IS CHARGED WITH A NEW SUPPLY OF SUBSTRATES TO BE SPUTTERED FILMS THEREON AND EVACUATED SO THAT THE LASTMENTIONED PRELIMINARY CHAMBER IS READY FOR A SUBSEQUENT   SPUTTERING CYCLE WHEREBY SUBSTRATES ARE CONTINUOUSLY SPUTTERED.

1973 TSUNEHIKO ENDO 3,776,830

PROCESS FOR PRODUCING SPUTTERED FILMS Filed July 9, 1971 INVENTOR.

' 3,776,830 PROCESS FOR PRODUCING SPUTTERED FILMS Tsunehiko Endo, 1716 Yahara Z-chome, Nerima-ku, Tokyo, Japan Filed July 9, 1971, 'Ser. No. 161,168 Int. Cl. C23c 15/00 US. Cl. 204-192 7 Claims ABSTRACT OF THE DISCLOSURE A process for producing sputtered films and an apparatus for carrying out said process in which substrates are transferred between a sputtering chamber and one of at least two preliminary chambers both of which sputtering and one preliminary chambers are maintained under the same pressure and gas atmospheric conditions, said substrates are sputtered films thereon while they are disposed in the sputtering chamber and during the transfer and sputtering of said substrates the other of said preliminary chambers is charged with a new supply of substrates to be sputtered films thereon and evacuated so that the lastmentioned preliminary chamber is ready for a subsequent sputtering cycle whereby substrates are continuously sputtered.

BACKGROUND OF THE INVENTION This invention relates to a process for producing a metallic or insulative film on a substrate by sputtering or depositing metal or insulative material against and on the substrate and an apparatus for carrying out the process.

It has been known in the art that a metallic thin film can be produced by the so-called cathode sputtering process and that an insulative film can be processed by the socalled high frequency sputtering process. The sputtered metallic films find their applications in various fields such as resistor layers for electric resistors and electrodes for capacitors. The sputtered insulative films find their application in the field of dielectric films for capacitors.

According to the cathode sputtering process, after a sputtering chamber has been substantially evacuated, the chamber is supplied with inert gas such as argon gas of high purity and a substrate is disposed betweenan anode and a cathode positioned within the chamber. An electric glow discharge takes place across the anode and cathode over the substrate whereby the material of the cathode is sputtered against the substrate. This process has been known suitable for obtaining a film of high melting point. When a sputtering operation is carried out by this process, if the sputtering chamber is evacuated to an insufficient degree for properly performing the sputtering and and chamber is maintained at such an insufficiently low degree of vacuum, when the cathode sputtering process is employed, the obtained film will inevitably contain impurities therein. Therefore, the sputtering chamber is required initially to have a vacuum degree range on the order of LO 10 torr. However, even if such a vacuum degree range is selected, since there is still the tendency that the obtained film contains impurities only at an initial stage of a successive operation, it has been generally followed that a pro-sputtering is initially conducted on a substrate in the sputtering chamber to remove impurities from the environment within the chamber prior to the subsequent proper sputtering and the proper sputtering operation is then conducted on subsequent successive substrates to form films thereon.

So far as the inventor knows there have been proposed no effective apparatus for producing sputtered films on a mass production scale or if any, such apparatus are very expensive in manufacture and operation. In a prior art sputtering apparatus which is designed to experimentally nitecl States Patent produce sputtered films, an exhausting or evacuating operation and a pre-sputtering operation have to be performed as each cycle of sputtered film production is carried out. Furthermore, it takes about 30 minutes-2 hours to attain a desired or predetermined degree of vacuum depending upon the volume of the sputtering chamber and/or the capacity of the vacuum pump employed in the sputtering apparatus and the pre-sputtering operation has to be performed over a time interval of 30 minutesl hour whereas it takes only 5-60 minutes to carry out the proper sputtering operation. Thus, it will be appreciated that the preparation period in a cycle of sputtered film production operation accounts for a substantial portion of the production cycle. Therefore, in the prior art sputtering apparatus the down time is substantially long during which the operation on the apparatus has to be halted for taking film-sputtered products out of the sputtering chamber and for charging a new supply of substrates to be sputtered films thereon into the sputtering chamber and as a result, the productivity of the sputtering apparatus is very low.

An improved sputtering apparatus for producing sputtered films successively has been proposed in which substrates to be deposited films thereon are successively passed through a series of chambers or passageways the degree of vacuum in which increases stepwise to the sputtering chamber and treated or film-deposited substrates are taken out of the sputtering chamber and passed through a series of chambers or passageways the degree of vacuum in which decreases stepwise to the atmosphere. However, this type of sputtering apparatus still has the disadvantages that evacuation means has to be provided in each of the chambers or passageways, the entire apparatus is massive and expensive and that the apparatus fails easily.

SUMMARY OF THE INVENTION Therefore, one principal object of the present invention is to provide a process for producing sputtered films which can successively deposit films on substrates without the necessity for use of a plurality of chambers or passageways the degree of vacuum in which varies stepwise.

Another object of the present invention is to provide a novel and improved apparatus for depositing material on substrates by sputtering process.

According to one aspect of the present invention, the sputtering apparatus comprises one sputtering chamber and at least two preliminary chambers in which substrates are sputtered material thereon as they are transferred between the sputtering chamber and one of the preliminary chambers both of which are maintained under the same vacuum and atmospheric conditions and simultaneously, the other preliminary chamber is opened to the atmosphere for receiving a new supply of substrates to be deposited films thereon or replacing substrates which have been deposited films thereon in the preceding sputtering operation by a new supply of substrates being followed by evacuation of the other chamber to a predetermined degree of vacuum thereby to make the other chamber ready for a next cycle of sputtering operation.

After all the substrates of the first-mentioned preliminary chamber have been deposited films thereon, the preliminary chamber is shut off the sputtering chamber and the second-mentioned preliminary chamber is then communicated with the sputtering chamber the interior of which is maintained under vacuum conditions and substrates are passed between the sputtering chamber and second-mentioned preliminary chamber to perform a cycle of material sputtering operation on the substrates and simultaneously, the first-mentioned preliminary chamber is opened to the atmosphere for replacing the film-deposited substrates by a new supply of substrates and then evacuated to the predetermined degree of vacuum ready for a further cycle of sputtering operation.

In this way, substrates are transferred between the sputtering chamber and one of the preliminary chambers and simultaneously, substrate replacing and evacuation operations are performed with the other preliminary chamber.

According to the present invention, there is provided a process for producing sputtered films successively comprising the steps of maintaining a sputtering area and one of at least two preliminary chambers at the same gas atmosphere under the same pressure conditions, transferring selected ones of a supply of substrates from said one preliminary chamber to said sputtering chamber, sputtering material against said selected substrates at said sputtering area within the sputtering chamber to deposit said material on the substrates when the substrates are positioned in the sputtering chamber, returning said sputtered substrates to said one preliminary chamber, repeating said two preceding steps until all of said supply of substrates from the one preliminary chamber are sputtered, charging a new supply of substrates into the other of said two preliminary chambers while said three preceding steps are being conducted, after said last-mentioned step and during said first three preceding steps, highly evacuating said second-mentioned preliminary chamber before the completion of sputtering against the substrates from said first-mentioned preliminary chamber, after the completion of sputtering against all the substrates from said first-mentioned preliminary chamber, shutting the preliminary chamber off said sputtering chamber and immediately thereafter, communicating said evacuated second-mentioned preliminary chamber with said sputtering chamber for sputtering said material against the substrates from the preliminary chamber whereby the sputtering operation is continuously carried out.

According to the present invention, there is also provided an apparatus for carrying out the process which comprises a sputtering chamber having a sputtering area containing an anode and a cathode across which a glow discharge takes place, at least two preliminary chambers for receiving a supply of substrates on which films are to be deposited, respectively, passage way means for communicating between said sputtering chamber and one of said preliminary chambers, said passage way means also serving to communicate between said chambers in a gas flow relationship while maintaining the chambers under the same gas atmosphere conditions, a high vacuum system for highly evacuating each of said chambers, a low vacuum system for evacuating said sputtering chamber as the chamber operates for sputtering, a gas supply for providing each of said chambers with inert gas, first conduit means for communicating said high vacuum system with each of said chambers, second conduit means for communicating said low vacuum system with said sputtering chamber, third conduit means for communicating said gas supply with each of said chambers, a voltage source for applying a high voltage across said anode and cathode at said sputtering area and valve means provided in said passage way means and first to third conduit means in association with each of said chambers, said valve means in the passage way means being selectively operated to communicate one of said preliminary chambers with said sputtering chamber and simultaneously shutting the other preliminary chamber off the sputtering chamber, whereby substrates are in succession transferred between one of said preliminary chambers and said sputtering chamber for sputtering material thereon and at the same time a new supply of substrates are charged into the other preliminary chamber and the last-mentioned chamber is maintained at a high vacuum degree ready for a subsequent cycle of sputtering operation through the valve means in the first conduit means.

The above and other objects and attendant advantages of the present invention will be more readily apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawing which shows a preferred embodiment of thin sputtered film producing apparatus in which the present invention is incorporated for illustration purpose only, but not for limiting the scope of the same in any way.

BRIEF DESCRIPTION OF THE DRAWING PREFERRED EMBODIMENT OF THE INVENTION The present invention will be now described referring to the accompanying drawing and more particularly, to FIG. 1 thereof in which a preferred embodiment of sputtered film producing apparatus of the invention is schematically shown. The apparatus is shown as comprising a sputtering chamber A and two preliminary chambers B and C. The opposite sides of the sputtering chamber A are in fluid communication with the two preliminary chambers B and C by means of conduits or passage ways 1 and 1' which extend between the opposite sides of the sputtering chamber and preliminary chambers and have valves V1 and V1 therein, respectively.

Disposed within the sputtering chamber A is an anode 20 which may be conveniently formed of stainless steel and a cathode 21 which may be formed of tantalum, niobium or the like which is sputtered material as desired and these electrodes are positioned one upon another in a vertically spaced relationship. The material from the cathode 21 is adapted to be sputtered against a substrate which is preferably formed of a glass plate sold under the trade name Corning 7059, a ceramic or a porcelain such as forsterite, mullite or alumina as desired on which a sputtered film is to be produced in the manner as will be described hereinafter. The anode 20 and cathode 21 are connected to a suitable high voltage source (not shown). The voltage to be employed in AC or DC ranging from 1,000 v. to 15,000 v. When AC voltage is employed, the voltage may be preferably an asymmetrical AC voltage.

Disposed within the preliminary chamber B is a vertically movable substrate supporting framework 2 having a plurality of vertically spaced shelves inwardly extending on the opposite inner surfaces thereof to support a plurality of trays in a vertically spaced relationship independently of each other each of which trays carries a plurality of substrates formed of the above-mentioned material thereon in a side-by-side spaced relationship. Similarly, the preliminary chamber C has a similar substrate supporting framework 2' disposed therein having the same construction as the framework 2. A plurality of trays each carrying a plurality of similar substrates in the same manner as mentioned in connection with the preliminary chamber B are supported in the framework 2. The frameworks 2 and 2' have posts or bearing rods 2a and 2a at the lower ends respectively, which extend downwardly through the bottom walls of the respectively associated chamber in an air-tight relationship thereto and move vertically so as to impart a vertical movement to the frameworks as the rods move vertically. Each framework is so designed that the framework is intermittently lowered in timed relationship to a particular cycle of sputtering operation to be carried out in the apparatus so as to position the succeeding lowermost trays in the plane where the conduits or passageways 1 and 1' lie in the manner as will be described hereinafter. The movement of the frameworks 2 and 2' is effected by a prime mover such as an oil-pressure-operated cylinder (not shown), for example, which is provided for each of the frameworks. Each of the preliminary chambers B and C is provided on the top with an access door (not shown) which is normally closed in an air-tight by a cover (not shown) and through which the framework is placed into and taken out of the preliminary chamber for replacing the treated or film-sputtered substrates by a new supply of substrates to be sputtered.

A gas bomb G is provided for supplying an inert gas such as argon and the gas under pressure from the bomb is passed through a valve V3, a gas pressure regulator R and a gas flow meter M into a conduit 41 from where the gas enters a purifier PR at the inlet thereof and issues from the purifier at the outlet thereof. The gas from the purifier is then passed to a conduit 42 the other end of which is communicated through valves V4, V5 and V6 with the gas inlets of the chambers A, B and C, respectively.

There is provided a high vacuum system H for evacuating the chambers and the system includes an oil diffusion pump DP and an oil rotary pump PR1. The system H is communicated through a conduit 7 having a valve V7 with the chamber A and through conduits 8 and 9 having valves V8 and V9, respectively, with the chambers B and C, respectively. The suction port in the oil diffusion pump DP is communicated with the conduits 7, 8 and 9 whereas the exhaust port in the diffusion pump is communicated through a conduit 14 having a valve V14 with the oil rotary pump PR1. I

Before a high range of vacuum is provided in the chambers, it is necessary to rapidly evacuate the chambers. For the purpose, a rapid evacuation system L provided with an oil rotary pump PR3 of higher exhaust capacity is provided. The pump PR3 is communicated through conduits 11, 12 and 13 which have valves V11, V12 and V13, respectively, with the chambers A, B and C, respectively.

The rapid evacuation system L serves to evacuate the chamber from the atmospheric pressure to the order of 1()- ltorr whereas the high vacuum system H serves to evacuate the chamber from the order of lO- 10 torr to the order of 1() torr.

In order to maintain the exhaust pressure of the inert gas on the order of l0 10" torr within the sputtering chamber during a successive sputtering operation thereon, a lower vacuum system L including a mechanical booster pump MBP and an oil rotary pump PR2 is provided. The booster pump MBP is communicated through a conduit 10 having a valve V10 with the sputtering chamber A.

Prior to initiation of the sputtering operation, the cover which closes the open top of the preliminary chamber B is first removed and thereafter, the sputtering framework 2, which supports a plurality of trays each of which in turn supports a plurality of substratesin the manner mentioned above, is placed into the chamber B. After the framework 2 has been placed in the chamber B, the top cover is replaced on the top of the chamber to seal the latter. Thereafter, the valves V1, V11 and V12 are opened to operate the rapid evacuation system L whereby the preliminary chambers B and C are rapidly evacuated. Then, the valves V11 and V12 are closed whereas the valves V7 and V8 are opened to operate the higher vacuum system H whereby the chambers A and B are further rapidly evacuated to the oder of l0 10- torr. When the pressure reaches the predetermined value, the valves V7 and V8 are closed to stop the operation of the higher vacuum system H whereas the valves V3, V4 and V5 are opened whereby inert gas such as argon gas is allowed to flow at a predetermined rate through the regulator R, flow meter M, conduit 41, gas purifier PR, conduit 42, valves V4 and V5 which are now open to the chambers A and B. Simultaneously, the valve V10 is opened to operate the booster pump MBP and oil rotary pump RPZ of the lower evacuation system L whereby the degree of vacuum within the chamber A is maintained on the order of 10 --10 torr. At this time, since the chamber B is in communication with the chamber A by means of the conduit 1, the chamber B is maintained at the same degree of vacuum as the chamber A.

Referring to FIG. 2 of the accompanying drawing, in this figure the chambers A and B are shown as being maintained at 10- -10 torr of inert gas at which the proper sputtering operation is conducted. It is preferable to conduct a pre-sputtering operation prior to the initiation of the proper sputtering operation. The pre-sputtering operation is achieved by transferring one tray on which no substrate is supported from the chamber B through the passage way 1 onto the anode 20 in the sputtering chamber A and then applying a high voltage across the anode and cathode 20 and [21. The pre-sputtering operation is carried out only before the proper sputtering operation which is to be carried out continuously is initiated and for the purpose of disclosure herein, the empty tray which is to be employed in the above-mentioned pre-sputtering operation is the lowermost tray of the trays supported on the framework 2. As shown in FIG. 3, the transfer of the empty tray from the chamber B to the chamber A is effected by means of a fork-shaped feed bar 3 which engages and holds the empty tray and then places the tray on the anode 20. As the feed bar 3 transfers the empty tray, the bar is first advanced by a suitable drive means (not shown) until the bar engages and holds the tray and then the feed bar is further advanced through the passage 1 to the chamber A until the tray reaches a position just above the anode 20 whereupon the feed bar 3 releases the tray to allow the latter to seat on the anode. After the tray has been placed on the anode, the feed bar is retracted from the chamber A carrying the tray thereon. The pre-sputtering operation is carried out over a time interval ranging from 30 minutes to 1 hour whereupon the bar is advanced from the chamber B to the chamber A and then retracted from the chamber A through the passage 1 into the chamber B until the tray is again received in the framework 2. Thereafter, the feed bar releases the tray to allow the tray to remain in the framework. Thereafter, the post 2a and accordingly, the framework 2 supported thereby is lowered by a distance corresponding to the vertical space between adjacent two trays and the feed bar 3 is again advanced until the bar engages and holds the second lowermost tray or the tray having a plurality of substrates thereon positioned just above the lowermost tray. The feed bar 3 which holds the next tray is further advanced through the passage 1 to the sputtering chamber A until the tray is held on the anode 20 in the sputtering chamber A whereupon the feed bar is retracted from the chamber A to the original position. Thereafter, a cycle of proper sputtering operation is conducted over a predetermined time interval by the high voltage applied across the anode and cathode which sputters metal from the cathode against the substrates on the tray to produce films thereon. After the films have been produced on the substrates on the second lowermost tray, the feed bar 3 is again advanced through the conduit 1 into the sputtering chamber A until the bar engages and holds the tray and then retracted to the original position in the chamber B. The same procedure is repeated until all the substrates on the trays which are now supported in the framework 2 are sputtering-treated.

While the substrates on the trays are being transferred between the sputtering and preliminary chambers A and B and sputtered in the sputtering chamber A in the manner mentioned above, the other preliminary chamber C is charged with the framework 2' in which a plurality of trays each carrying a plurality of substrates to be sputtered through the top of the chamber which has been now uncovered and the chamber is evacuated to the order of IO- IO- torr. This is carried out by opening the valve V13 to operate the lower vacuum system L until the vacuum degree in the chamber C reaches the order of IO- IO- torr whereupon the lower vacuum system ceases to operate and the valve V13 is closed whereas the valve V9 is opened to operate the higher vacuum system H to evacuate the chamber C to the order of H -ltorr and the chamber is then maintained at the vacuum degree until the substrates on all the trays in the preliminary chamber B are formed thereon with films from metal of the cathode 21. In this way, the substrates on all the trays in the chamber C are ready for sputtering treatment while a cycle of sputtering operation is being conducted on the substrates of the chamber B and upon the termination of the cycle on the substrates of the chamber B has been completed, a successive sputtering operation is conducted on the substrates of the chamber C.

After all the substrates of the chamber B have been formed thereon with films in the manner mentioned above, the valves V1 and V3 are closed to shut the preliminary chamber B 011?, the sputtering chamber A and the valves V1 and V6 are opened whereas the valve V9 is closed whereupon the next cycle of metal sputtering operation is conducted on the substrates of the preliminary chamber C. Since inert gas at l0'- -l0 torr continues to flow through the sputtering chamber A when the sputtering operation is shifted from the chamber B to the chamber C, the sputtering operation can be immediately initiated on the substrates of the chamber C without any time delay.

While the cycle of sputtering operation is being conducted on the substrates of the chamber C, the top of the chamber B is uncovered to expose the interior of the chamber to the atmosphere and the framework 2 supporting the trays the substrates on which have been deposited with metal is taken out of the chamber B through the new uncovered top thereof for replacing the treated substrates for a new supply of substrates. After the new supply of substrates have been positioned on the respective trays supported in the framework in the manner mentioned above, the framework is again charged into the chamber B and the chamber is then evacuated to the order of 10- torr and maintained at the vacuum degree ready for a next cycle of sputtering operation for the new supply of substrates.

The exhaust port of the rotary pump PR2 which is adapted to continuously operate during a cycle of sputtering operation may be communicated through a conduit 43 (shown with the dotted line in FIG. 1) with a second inlet of the gas purified PR and this arrangement is economical because the inert gas which was used in the preceding cycle can be reused for a succeeding cycle.

In a practical sputtering operation on the sputtering apparatus of the present invention, glass plates sold under the trade name Corning 7059 were deposited with tantalum. The cathode comprised tantalum which was the material to be deposited and the anode comprised stainless steel. Each of the glass plates was 50 mm., by 50 mm., with 0.8 mm. thickness. One tray carried 60 substrates thereon and 16 trays were stacked in one framework. Each chamber was initially rapidly evacuated to the order of 1x l0- torr over a time interval of about minutes and then shifted to the higher vacuum system to be evacuated to the order of 1.6 10- torr. over a time interval of about 60 minutes. A pre-sputtering operation was conducted by allowing argon gas to flow through the sputtering chamber A while maintaining the chamber at 3 10- torr as the lower vacuum system operates and thereafter, the proper sputtering was conducted. The time interval for the proper sputtering varied within the range of 5-60 minutes depending upon desired sheet resistance values and temperature coefiicients. Thus, it took at least 100 minutes to deposit metal on all the substrates of one preliminary chamber and when one preliminary chamber is charged with a new supply of substrates while a cycle of proper sputtering operation is being conducted between the sputtering chamber and the other preliminary chamber, a sufiicient time was obtained for rapidly evacuating.

In the foregoing, although one embodiment of the invention which is considered best at present time has been illustrated and described, it will be apparent to those skilled in the art that the same is illustrative in nature and may be embodied in various other different modes other than the illustrated one within the scope and without departing from the spirit of the invention. For example, when all the substrates of one preliminary chamber is deposited with metal by sputtering over a relatively short time interval, three or more preliminary chambers may be provided to be successively operated for sputtering. In this way, it will be appreciated that the sputtering apparatus of the invention is less expensive as compared with the prior art sputtering apparatus in which a plurality of preliminary chambers of different degrees of vacuum are provided on the inlet and outlet sides of the sputtering chamber. Furthermore, inert gas such as argon may be added thereto one or more reactive gases selected from the group comprising N 0 and OH; to provide nitride, oxide and/ or carbonate films. The present invention intend to broadly include such and all other modifications which may fall within the scope of the appended claims.

What is claimed is:

1. A process for producing films on substrates by sputtering comprising the steps of (a) maintaining one sputtering chamber having a sputtering area and a first of at least first and second preliminary chambers at the same gas atmosphere and under the same pressure conditions,

(b) transferring selected ones of a supply of substrates from said first preliminary chamber to said sputtering chamber,

(0) sputtering material against said selected substrates at said sputtering area within the sputtering chamber to deposit said material on the substrates when the substrates are positioned in the sputtering chamber,

(d) returning said sputtered substrates to said first preliminary chamber,

(e) repeating said three preceding steps with dilferent ones of the supply of substrates until all of said supply of substrates from said first preliminary chamber are sputtered,

(f) charging a new supply of substrates into said second preliminary chamber while said four preceding steps are being conducted,

(g) highly evacuating said second preliminary chamber after said step (f) and during said (b) through (e) steps and before the completion of sputtering against the substrates from said preliminary chamber,

(h) shutting olf said one preliminary chamber from said first sputtering chamber after the completion of sputtering against all the substrates from said first preliminary chamber and immediately thereafter,

(1) communicating said evacuated second preliminary chamber with said sputtering chamber for sputtering said material against the substrates from the second preliminary chamber whereby the sputtering operation is continuously carried out.

2. The process as set forth in claim 1 in which each preliminary chamber removably receives a framework which supports a plurality of trays in a vertically spaced relationship each of which in turn supports a plurality of substrates thereon in a laterally spaced relationship and in which one tray at a time is transferred between said sputtering and one of the preliminary chambers.

3. The process as set forth in claim 1, in which said framework is intermittently moved in a vertical direction by a distance corresponding to the vertical space between two adjacent trays whereby one tray at a time is transferred to said sputtering chamber for sputtering.

4. The process as set forth in claim 1, in which said transfer of substrates between said sputtering chamber and one of said preliminary chambers is effected by a feed bar which moves reciprocally in a horizontal plane and engages and holds one tray at one time.

5. The process as set forth in claim 1, including (j) transferring selected ones of a supply of substrates from said second preliminary chamber to said sputtering chamber,

(k) sputtering material against said selected substrates at said sputtering area Within the sputtering chamber to deposit said material on the substrates when the substrates are positioned in the sputtering chamber,

(1) returning said sputtered substrates to said second preliminary chamber,

(In) and repeating said steps (j), (k), and (l) with different ones of the supply of substrates until all said supply of substrates from said second preliminary chamber are sputtered.

6. The process as set forth in claim 5 including (11) charging a new supply of substrates into said first pre- 10 liminary chamber while said steps (j), (k), (l), and (m) are being conducted.

7. The process as set forth in claim 6 including evacuating said first preliminary chamber after said step (11) and during said steps (j), (k), (1), and (m) and before the completion of sputtering against the substrates from said second preliminary chamber.

References Cited UNITED STATES PATENTS 2,746,420 5/1956 Steigerwald 11849.5 3,340,176 9/1967 Belluso et al 204298 3,661,759 5/1972 Bruce et a1. 204192 3,206,322 9/ 1965 Morgan 204192 JOHN H. MACK, Primary Examiner D. R. VALENTINE, Assistant Examiner 

